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  1. using System;
  2. using System.Collections.Generic;
  3. using System.Linq;
  4. using System.IO;
  5. using System.Text;
  6.  
  7. namespace RegexGenerator
  8. {
  9.     class RegexGenerator
  10.     {
  11.         // For simplicity's sake, we'll limit the options to to 7-bit ASCII.
  12.         static char[] _allPrintableChars = null;
  13.         static char[] AllPrintableChars
  14.         {
  15.             get
  16.             {
  17.                 if (_allPrintableChars == null)
  18.                     _allPrintableChars = Enumerable.Range(32, 127 - 32).Select(i => (char)i).ToArray();
  19.                 return _allPrintableChars;
  20.             }
  21.         }
  22.  
  23.         struct Path
  24.         {
  25.             public char Value;
  26.             public List<Path> NextState;
  27.  
  28.             public Path(char value, List<Path> nextState)
  29.             {
  30.                 Value = value;
  31.                 NextState = nextState;
  32.             }
  33.         }
  34.  
  35.         static Random Rand = new Random(); // random generator
  36.  
  37.         List<Path> startState;
  38.  
  39.         RegexGenerator(string regex)
  40.         {
  41.             startState = new List<Path>();
  42.  
  43.             var currentState = startState;
  44.  
  45.             using (StringReader sr = new StringReader(regex))
  46.             {
  47.                 char[] pathValues;
  48.                 while (GetNextValueSet(sr, out pathValues))
  49.                 {
  50.                     var newState = new List<Path>();
  51.  
  52.                     int nextChar = sr.Peek();
  53.                     if (nextChar == '*')
  54.                     {
  55.                         sr.Read();
  56.                         currentState.Add(new Path('\0', newState));
  57.                         currentState.AddRange(pathValues.Select(c => new Path(c, currentState)));
  58.                     }
  59.                     else
  60.                     {
  61.                         currentState.AddRange(pathValues.Select(c => new Path(c, newState)));
  62.  
  63.                         if (nextChar == '+')
  64.                         {
  65.                             sr.Read();
  66.                             currentState = newState;
  67.                             currentState.AddRange(pathValues.Select(c => new Path(c, currentState)));
  68.  
  69.                             newState = new List<Path>();
  70.                             currentState.Add(new Path('\0', newState));
  71.                         }
  72.                     }
  73.                     currentState = newState;
  74.                 }
  75.             }
  76.         }
  77.  
  78.         bool GetNextValueSet(StringReader sr, out char[] pathValues)
  79.         {
  80.             int c = sr.Read();
  81.             switch (c)
  82.             {
  83.                 case -1: pathValues = null; return false;
  84.  
  85.                 default: pathValues = new char[] { (char)c }; return true;
  86.  
  87.                 case '\\':
  88.                     c = AssertRead(sr, "Pattern ends in trailing backslash.");
  89.                     goto default;
  90.  
  91.                 case '*':
  92.                 case '+':
  93.                     throw new Exception("Syntax error: Invalid character  ('" + (char)c + "')");
  94.  
  95.                 case '.':
  96.                     pathValues = AllPrintableChars;
  97.                     return true;
  98.  
  99.                 case '[':
  100.                     List<char> charlist = new List<char>();
  101.                     while ((c = AssertRead(sr, "Missing close bracket.")) != ']')
  102.                     {
  103.                         if (c == '\\')
  104.                             c = AssertRead(sr, "Pattern ends in trailing backslash.");
  105.  
  106.                         int nextChar = sr.Peek();
  107.                         if (nextChar == -1)
  108.                             throw new Exception("Syntax Error: Missing close bracket.");
  109.  
  110.                         if (nextChar == '-') // add range
  111.                         {
  112.                             sr.Read();
  113.                             nextChar = sr.Read();
  114.  
  115.                             if (nextChar == ']')
  116.                             {
  117.                                 charlist.Add((char)c);
  118.                                 charlist.Add('-');
  119.                                 break;
  120.                             }
  121.                             else if (nextChar == '\\')
  122.                                 nextChar = AssertRead(sr, "Pattern ends in trailing backslash.");
  123.  
  124.                             if (nextChar < c)
  125.                                 throw new Exception("Syntax Error: Range out of order.");
  126.  
  127.                             charlist.AddRange(Enumerable.Range(c, nextChar - c + 1).Select(i => (char)i));
  128.                         }
  129.                         else
  130.                         {
  131.                             charlist.Add((char)c);
  132.                         }
  133.                     }
  134.                     pathValues = charlist.Distinct().ToArray();
  135.                     return true;
  136.             }
  137.         }
  138.  
  139.         int AssertRead(TextReader reader, string message)
  140.         {
  141.             int c = reader.Read();
  142.             if (c == -1)
  143.                 throw new Exception("Syntax error: " + message);
  144.             return c;
  145.         }
  146.  
  147.         string GenerateRandomPattern()
  148.         {
  149.             StringBuilder sb = new StringBuilder();
  150.  
  151.             var currentState = startState;
  152.             while (currentState.Count > 0)
  153.             {
  154.                 Path pathToTake = currentState[Rand.Next(currentState.Count)];
  155.                 if (pathToTake.Value != '\0')
  156.                 {
  157.                     sb.Append(pathToTake.Value);
  158.                 }
  159.                 currentState = pathToTake.NextState;
  160.             }
  161.  
  162.             return sb.ToString();
  163.         }
  164.  
  165.         static void Main(string[] args)
  166.         {
  167.             try
  168.             {
  169.                 var gen = new RegexGenerator("[A-Za-z0-9$.+!*'(){},~:;=@#%_\\-]*");
  170.                 Console.WriteLine(gen.GenerateRandomPattern());
  171.  
  172.                 gen = new RegexGenerator("ab[c-l]+jkm9*10+");
  173.                 Console.WriteLine(gen.GenerateRandomPattern());
  174.  
  175.                 gen = new RegexGenerator("iqb[beoqob-q]872+0qbq*");
  176.                 Console.WriteLine(gen.GenerateRandomPattern());
  177.             }
  178.             catch (Exception e)
  179.             {
  180.                 Console.WriteLine(e.Message);
  181.             }
  182.             //Console.Read();
  183.         }
  184.     }
  185. }
Success #stdin #stdout 0.01s 131712KB
comments (?)
stdin 
Standard input is empty
stdout 
sJagqL7A
abjcgcjkm10
iqbp87220qb
https://ideone.com/2FnDfi
language:
C# (gmcs 5.20.1)
created:
8 years ago
visibility:
public

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